Nanoporous Polystyrene Inverse Opal Materials with Optical Interference Properties for Label-Free Biosensing

Colloidal crystal nanomaterials have been proven to be valuable substrates for optical-based biosensing due to their ordered macroporous nanostructure and brilliant optical properties. In this work, silica colloidal crystal (SCC) thin films, as well as polystyrene–SCC composite films and inverse opal (IO) polystyrene films fabricated using SCC as templates, are investigated for their application as substrate materials in optical interferometric biosensors. The SCC films formed by the self-assembly of silica colloidal crystals have the most densely packed nano-3D structure, also known as the opal structure. IO films are fabricated by filling the opal pores of SCC with polystyrene and then removing the template, resulting in an interconnected nano-3D ordered macroporous structure, as indicated by the name inverse opal. The performance of the three materials was compared and discussed based on an ordered porous layer interferometry optical platform, focusing on refractive index response, protein adsorption response, and biomolecular interaction response. These results could potentially offer innovative material support for the advancement of label-free optical biosensors, which can be used for more biological/biochemical/biomolecular reaction monitoring studies.